/*

   * Basic general purpose allocator for managing special purpose
   * memory, for example, memory that is not managed by the regular
   * kmalloc/kfree interface.  Uses for this includes on-device special
   * memory, uncached memory etc.
   *
   * It is safe to use the allocator in NMI handlers and other special
   * unblockable contexts that could otherwise deadlock on locks.  This
   * is implemented by using atomic operations and retries on any
   * conflicts.  The disadvantage is that there may be livelocks in
   * extreme cases.  For better scalability, one allocator can be used
   * for each CPU.
   *
   * The lockless operation only works if there is enough memory
   * available.  If new memory is added to the pool a lock has to be
   * still taken.  So any user relying on locklessness has to ensure
   * that sufficient memory is preallocated.
   *
   * The basic atomic operation of this allocator is cmpxchg on long.
   * On architectures that don't have NMI-safe cmpxchg implementation,
   * the allocator can NOT be used in NMI handler.  So code uses the
   * allocator in NMI handler should depend on
   * CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG.

   *

   * Copyright 2005 (C) Jes Sorensen <jes@trained-monkey.org>
   *
   * This source code is licensed under the GNU General Public License,
   * Version 2.  See the file COPYING for more details.
   */

  #include <linux/slab.h>

  #include <linux/module.h>

  #include <linux/bitmap.h>

  #include <linux/rculist.h>
  #include <linux/interrupt.h>

  #include <linux/genalloc.h>

  static int set_bits_ll(unsigned long *addr, unsigned long mask_to_set)
  {
  	unsigned long val, nval;
  
  	nval = *addr;
  	do {
  		val = nval;
  		if (val & mask_to_set)
  			return -EBUSY;
  		cpu_relax();
  	} while ((nval = cmpxchg(addr, val, val | mask_to_set)) != val);
  
  	return 0;
  }
  
  static int clear_bits_ll(unsigned long *addr, unsigned long mask_to_clear)
  {
  	unsigned long val, nval;
  
  	nval = *addr;
  	do {
  		val = nval;
  		if ((val & mask_to_clear) != mask_to_clear)
  			return -EBUSY;
  		cpu_relax();
  	} while ((nval = cmpxchg(addr, val, val & ~mask_to_clear)) != val);
  
  	return 0;
  }
  
  /*
   * bitmap_set_ll - set the specified number of bits at the specified position
   * @map: pointer to a bitmap
   * @start: a bit position in @map
   * @nr: number of bits to set
   *
   * Set @nr bits start from @start in @map lock-lessly. Several users
   * can set/clear the same bitmap simultaneously without lock. If two
   * users set the same bit, one user will return remain bits, otherwise
   * return 0.
   */
  static int bitmap_set_ll(unsigned long *map, int start, int nr)
  {
  	unsigned long *p = map + BIT_WORD(start);
  	const int size = start + nr;
  	int bits_to_set = BITS_PER_LONG - (start % BITS_PER_LONG);
  	unsigned long mask_to_set = BITMAP_FIRST_WORD_MASK(start);
  
  	while (nr - bits_to_set >= 0) {
  		if (set_bits_ll(p, mask_to_set))
  			return nr;
  		nr -= bits_to_set;
  		bits_to_set = BITS_PER_LONG;
  		mask_to_set = ~0UL;
  		p++;
  	}
  	if (nr) {
  		mask_to_set &= BITMAP_LAST_WORD_MASK(size);
  		if (set_bits_ll(p, mask_to_set))
  			return nr;
  	}
  
  	return 0;
  }
  
  /*
   * bitmap_clear_ll - clear the specified number of bits at the specified position
   * @map: pointer to a bitmap
   * @start: a bit position in @map
   * @nr: number of bits to set
   *
   * Clear @nr bits start from @start in @map lock-lessly. Several users
   * can set/clear the same bitmap simultaneously without lock. If two
   * users clear the same bit, one user will return remain bits,
   * otherwise return 0.
   */
  static int bitmap_clear_ll(unsigned long *map, int start, int nr)
  {
  	unsigned long *p = map + BIT_WORD(start);
  	const int size = start + nr;
  	int bits_to_clear = BITS_PER_LONG - (start % BITS_PER_LONG);
  	unsigned long mask_to_clear = BITMAP_FIRST_WORD_MASK(start);
  
  	while (nr - bits_to_clear >= 0) {
  		if (clear_bits_ll(p, mask_to_clear))
  			return nr;
  		nr -= bits_to_clear;
  		bits_to_clear = BITS_PER_LONG;
  		mask_to_clear = ~0UL;
  		p++;
  	}
  	if (nr) {
  		mask_to_clear &= BITMAP_LAST_WORD_MASK(size);
  		if (clear_bits_ll(p, mask_to_clear))
  			return nr;
  	}
  
  	return 0;
  }

  /**
   * gen_pool_create - create a new special memory pool

   * @min_alloc_order: log base 2 of number of bytes each bitmap bit represents
   * @nid: node id of the node the pool structure should be allocated on, or -1

   *
   * Create a new special memory pool that can be used to manage special purpose
   * memory not managed by the regular kmalloc/kfree interface.

   */
  struct gen_pool *gen_pool_create(int min_alloc_order, int nid)

  {

  	struct gen_pool *pool;

  	pool = kmalloc_node(sizeof(struct gen_pool), GFP_KERNEL, nid);
  	if (pool != NULL) {

  		spin_lock_init(&pool->lock);

  		INIT_LIST_HEAD(&pool->chunks);
  		pool->min_alloc_order = min_alloc_order;
  	}
  	return pool;

  }
  EXPORT_SYMBOL(gen_pool_create);

  /**

   * gen_pool_add_virt - add a new chunk of special memory to the pool

   * @pool: pool to add new memory chunk to

   * @virt: virtual starting address of memory chunk to add to pool
   * @phys: physical starting address of memory chunk to add to pool

   * @size: size in bytes of the memory chunk to add to pool
   * @nid: node id of the node the chunk structure and bitmap should be
   *       allocated on, or -1

   *
   * Add a new chunk of special memory to the specified pool.

   *
   * Returns 0 on success or a -ve errno on failure.

   */

  int gen_pool_add_virt(struct gen_pool *pool, unsigned long virt, phys_addr_t phys,
  		 size_t size, int nid)

  {

  	struct gen_pool_chunk *chunk;
  	int nbits = size >> pool->min_alloc_order;
  	int nbytes = sizeof(struct gen_pool_chunk) +
  				(nbits + BITS_PER_BYTE - 1) / BITS_PER_BYTE;

  	chunk = kmalloc_node(nbytes, GFP_KERNEL | __GFP_ZERO, nid);

  	if (unlikely(chunk == NULL))

  		return -ENOMEM;

  	chunk->phys_addr = phys;
  	chunk->start_addr = virt;
  	chunk->end_addr = virt + size;

  	atomic_set(&chunk->avail, size);

  	spin_lock(&pool->lock);
  	list_add_rcu(&chunk->next_chunk, &pool->chunks);
  	spin_unlock(&pool->lock);

  
  	return 0;

  }

  EXPORT_SYMBOL(gen_pool_add_virt);
  
  /**
   * gen_pool_virt_to_phys - return the physical address of memory
   * @pool: pool to allocate from
   * @addr: starting address of memory
   *
   * Returns the physical address on success, or -1 on error.
   */
  phys_addr_t gen_pool_virt_to_phys(struct gen_pool *pool, unsigned long addr)
  {

  	struct gen_pool_chunk *chunk;

  	phys_addr_t paddr = -1;

  	rcu_read_lock();
  	list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk) {
  		if (addr >= chunk->start_addr && addr < chunk->end_addr) {
  			paddr = chunk->phys_addr + (addr - chunk->start_addr);
  			break;
  		}

  	}

  	rcu_read_unlock();

  	return paddr;

  }
  EXPORT_SYMBOL(gen_pool_virt_to_phys);

  /**
   * gen_pool_destroy - destroy a special memory pool

   * @pool: pool to destroy

   *
   * Destroy the specified special memory pool. Verifies that there are no
   * outstanding allocations.

   */
  void gen_pool_destroy(struct gen_pool *pool)
  {
  	struct list_head *_chunk, *_next_chunk;
  	struct gen_pool_chunk *chunk;
  	int order = pool->min_alloc_order;
  	int bit, end_bit;

  	list_for_each_safe(_chunk, _next_chunk, &pool->chunks) {
  		chunk = list_entry(_chunk, struct gen_pool_chunk, next_chunk);
  		list_del(&chunk->next_chunk);
  
  		end_bit = (chunk->end_addr - chunk->start_addr) >> order;
  		bit = find_next_bit(chunk->bits, end_bit, 0);
  		BUG_ON(bit < end_bit);
  
  		kfree(chunk);
  	}
  	kfree(pool);
  	return;
  }
  EXPORT_SYMBOL(gen_pool_destroy);

  /**
   * gen_pool_alloc - allocate special memory from the pool

   * @pool: pool to allocate from
   * @size: number of bytes to allocate from the pool

   *
   * Allocate the requested number of bytes from the specified pool.

   * Uses a first-fit algorithm. Can not be used in NMI handler on
   * architectures without NMI-safe cmpxchg implementation.

   */

  unsigned long gen_pool_alloc(struct gen_pool *pool, size_t size)

  {

  	struct gen_pool_chunk *chunk;

  	unsigned long addr = 0;

  	int order = pool->min_alloc_order;

  	int nbits, start_bit = 0, end_bit, remain;
  
  #ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
  	BUG_ON(in_nmi());
  #endif

  	if (size == 0)
  		return 0;

  	nbits = (size + (1UL << order) - 1) >> order;

  	rcu_read_lock();
  	list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk) {
  		if (size > atomic_read(&chunk->avail))
  			continue;

  
  		end_bit = (chunk->end_addr - chunk->start_addr) >> order;

  retry:
  		start_bit = bitmap_find_next_zero_area(chunk->bits, end_bit,
  						       start_bit, nbits, 0);
  		if (start_bit >= end_bit)

  			continue;

  		remain = bitmap_set_ll(chunk->bits, start_bit, nbits);
  		if (remain) {
  			remain = bitmap_clear_ll(chunk->bits, start_bit,
  						 nbits - remain);
  			BUG_ON(remain);
  			goto retry;

  		}

  
  		addr = chunk->start_addr + ((unsigned long)start_bit << order);

  		size = nbits << order;
  		atomic_sub(size, &chunk->avail);
  		break;

  	}

  	rcu_read_unlock();
  	return addr;

  }
  EXPORT_SYMBOL(gen_pool_alloc);

  /**
   * gen_pool_free - free allocated special memory back to the pool

   * @pool: pool to free to
   * @addr: starting address of memory to free back to pool
   * @size: size in bytes of memory to free

   *

   * Free previously allocated special memory back to the specified
   * pool.  Can not be used in NMI handler on architectures without
   * NMI-safe cmpxchg implementation.

   */
  void gen_pool_free(struct gen_pool *pool, unsigned long addr, size_t size)
  {

  	struct gen_pool_chunk *chunk;

  	int order = pool->min_alloc_order;

  	int start_bit, nbits, remain;

  #ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
  	BUG_ON(in_nmi());
  #endif

  	nbits = (size + (1UL << order) - 1) >> order;
  	rcu_read_lock();
  	list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk) {

  		if (addr >= chunk->start_addr && addr < chunk->end_addr) {
  			BUG_ON(addr + size > chunk->end_addr);

  			start_bit = (addr - chunk->start_addr) >> order;
  			remain = bitmap_clear_ll(chunk->bits, start_bit, nbits);
  			BUG_ON(remain);
  			size = nbits << order;
  			atomic_add(size, &chunk->avail);
  			rcu_read_unlock();
  			return;

  		}

  	}

  	rcu_read_unlock();
  	BUG();

  }
  EXPORT_SYMBOL(gen_pool_free);

  
  /**
   * gen_pool_for_each_chunk - call func for every chunk of generic memory pool
   * @pool:	the generic memory pool
   * @func:	func to call
   * @data:	additional data used by @func
   *
   * Call @func for every chunk of generic memory pool.  The @func is
   * called with rcu_read_lock held.
   */
  void gen_pool_for_each_chunk(struct gen_pool *pool,
  	void (*func)(struct gen_pool *pool, struct gen_pool_chunk *chunk, void *data),
  	void *data)
  {
  	struct gen_pool_chunk *chunk;
  
  	rcu_read_lock();
  	list_for_each_entry_rcu(chunk, &(pool)->chunks, next_chunk)
  		func(pool, chunk, data);
  	rcu_read_unlock();
  }
  EXPORT_SYMBOL(gen_pool_for_each_chunk);
  
  /**
   * gen_pool_avail - get available free space of the pool
   * @pool: pool to get available free space
   *
   * Return available free space of the specified pool.
   */
  size_t gen_pool_avail(struct gen_pool *pool)
  {
  	struct gen_pool_chunk *chunk;
  	size_t avail = 0;
  
  	rcu_read_lock();
  	list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk)
  		avail += atomic_read(&chunk->avail);
  	rcu_read_unlock();
  	return avail;
  }
  EXPORT_SYMBOL_GPL(gen_pool_avail);
  
  /**
   * gen_pool_size - get size in bytes of memory managed by the pool
   * @pool: pool to get size
   *
   * Return size in bytes of memory managed by the pool.
   */
  size_t gen_pool_size(struct gen_pool *pool)
  {
  	struct gen_pool_chunk *chunk;
  	size_t size = 0;
  
  	rcu_read_lock();
  	list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk)
  		size += chunk->end_addr - chunk->start_addr;
  	rcu_read_unlock();
  	return size;
  }
  EXPORT_SYMBOL_GPL(gen_pool_size);